The invention relates to a novel method for producing a phenolic resin.
It is known practice to make propulsion nozzles using phenolic resins of resol type, for example using an ablative resin such as the Ablaphene RS101 resin. The phenolic resins used for this application must have excellent carbonizing and heat stability properties.
The phenolic resins such as the Ablaphene RS101 resin are synthesized from formaldehyde and phenol. It is known that formaldehyde is very reactive with respect to phenol. The phenolic resins synthesized from these two compounds have high aromatic densities and high crosslinking densities, which gives the resins the desired carbonizing and heat stability properties.
However, formaldehyde and phenol are compounds categorized as category 1B and 2 carcinogenic, mutagenic, reprotoxic (CMR), respectively.
Because of its toxicity, formaldehyde is a chemical compound of which the use becomes strictly regulated by CMR legislation. Furthermore, formaldehyde is a chemical compound derived from exhaustible fossil resources.
Several studies on the synthesis of phenolic resins from aldehyde compounds derived from renewable resources and without formaldehyde have been carried out. The formaldehyde is then replaced with aldehyde compounds such as glyoxal [E. C. Ramires, J. D. Megiatto, C. Gardrat, A. Castellan, E. Frollini, Biobased composites from glyoxal-phenolic resins and sisal fibers, Bioresour. Technol., 101 (2010) 1998-2006.] or furfural [L. H. Brown, Resin-forming reactions of furfural and phenol, J. Ind. Eng. Chem., 44 (1952) 2673-2675.] for example. These compounds are less reactive than formaldehyde and can result in the obtaining of phenolic resins which have carbonizing and heat stability properties that are insufficient for producing aeronautical parts such as propulsion nozzles. Furthermore, these compounds, although they are less toxic than formaldehyde, are nevertheless categorized as CMR 2.
Also known is document US 2010/316555 which describes the preparation of a phenolic resin by reaction between a compound having a methylol function and an aldehyde.
There is thus a need to have a novel route of synthesis of phenolic resins which makes it possible to dispense with the use of formaldehyde or other aldehyde compounds categorized as CMR.
There is also a need to have a novel route of synthesis of phenolic resins which have carbonizing and heat stability properties that are suitable for producing aeronautical parts such as propulsion nozzles.